One known strongly basic catalyst used, for example, in the isomerization of olefins is an alkali metal-supported substance prepared by depositing an alkali metal on a carrier having a high specific surface area such as active alumina (see Japanese Patent Publication No. 24138/1970). This substance has high catalytic activity but is very unstable, and even when meticulous cares are taken in its preparation, storage, operational treatments, etc., it cannot show stable catalytic performance.